Great Lakes annual maximum ice coverage 1973-2021

Ice cover on the Great Lakes can fluctuate dramatically from year to year, depending on several patterns of climate variability. Years with lower-than-normal ice cover appear to have become more frequent during the past two decades. The graph indicates that 1979 was the year with the highest ice coverage (94.7%), while 2002 had the lowest maximum ice coverage (11.8%) meaning that the Great Lakes were almost ice-free for the entire year.